Steve,

You introduce alot of conditions in your question :

Let me see :

-1- my understanding of engineering principles and Physical laws. (some would say that this is non existant, but how dependable are they)

-2- Present craft designs, does this include or excludes prototypes and experimental craft ? Does this limit the question to boats like the Tornado H16 or may M20 and M18 for example also be included ?

-3- B class catamarans. This means that Supercats and sorts are not allowed in me answering your question. Especially the big boys like ARC 27.

-4- all conditions on the water (trailered over the freeway is out) , excluding being aided surfing down a wave.


Now before I answer your question and I will I would like to state ones again what I said in teh post that sparked this Speed trails thread.

What I said was :"
...
In light winds cat can reach speed closing to 2 times the windspeed when under spinaker on their optimal course. After that the ratio just drops. Often teh ratio is only 1.5 or less.

Normal beachcat normally sail no faster than the windspeed with a maximum of just over 50 km/hour = 30 knots."

So I say that a beachcat (in the upper spectrum of the windspeed range) can be expected to sail at about the windspeed. This means that say a Tornado in about 20 knots of wind would go about 20 knots and and so on. This would be consistant with the average 23 knots at the speedtrails if these were held in somethin like 20 to 25 knots.

Than I continued with the comment ;"with a maximum of just over 50 km/hour = 30 knots" which is there to indicate that the rule of thumb of topspeed = windspeed in the stronger winds is limited. With this I indicated that a beach cat will not go 40 knots in winds of 40 knots.

I also consider for example the ARC 27 and M18 beachcats despite them being rare and I do define sailing as :"being propelled by natural energy sources". The last includes favourable waves but excludes currents as this first will increase waterspeed but the last doesn't. For these two reason I named the limit of 30 knots for all-out (water) speed of a beach catamaran. And I have no doubt that this speed is reach from time to time under favourable conditions.

By this I answered the question "What is the fastest recorded speed on a beach cat and how fast do cats go compared to the windspeed."

The question wasn't what was the highest average speed recorded over 500 mtr. at an official speed trail ? Nor did it limit the answers to only B-class cats, solely windpower or even mainstream cats.

But to answer part of your question (the main answer will come shortly):

I am totally convinced that even a design made to the B-class specs is capable of reaching higher speeds than 23 knots due to solely windpower. Do this mind experiment : If a standard tornado (singel trap ?) reach the top average speed of 23 knots at an official speed trail than a modified tornado platform of say 125 kg's (carbon) with a rig completely optimized for reaching (shorter mast with fuller cut main and fuller cut jib with double trapezes will undoubtly go faster than 23 knots. On AVERAGE and is very likely to show momentary bursts of speed even higher than that.

But to get the really max out a B-class boat I would lengthen a nacra 5,7 hull and make the hulls out of carbon, use 18 sq. beams to make it 3,05 mtr. wide and put a 8,5 mtr. Taipan (4.9 or 5.7) wing mast with a large high aspect jib on it, optimize the sails for reaching, find a light crew and cream that standard Tornado recording.

Now lets introduce your last limit "present craft design"

This one is more tricky as the better designed boats are often not compliant with B-class rules or when they are they are often fully optimized for windward/leeward sailing. The last means these designs have sacrifized (topspeed) reaching speed for pointing ability and high VMG's. This quickly reduces the choice to a few boats.

Tornado (new version), Nacra 5,7 (with raised boards), Taipan 5,7, Dart 20.

I think that an exellent crew (Booth, Bundock, etc) on of these boats with optimized sails for reaching may well be able to crank that record a few knots higher on wind power alone.

So the answer to your question :"would you confirm that your understanding of engineering principles and physical laws state that present craft designs are limited in speed to about 23kts for b class cats, that would apply to all conditions (on water) except one wave events?"

Would be "NO" I would not confirm that. The way you have phrased your question ofcourse has limited the extra gain that can be made that is true. Therefor 23 knots will be close. But when you allow more freedom in designing there is no engineering or physical reason why a displacement catamaran should be unable to reach considerable higher speeds. It will get alot harder with every knot that is true but not impossible.

I hope this answers your question fully as well as those of others.

To give a real life example. Nobody thought that 16 footers would be able to considerably faster than a H16 ot Nacra 5.0 until a lone lightweight Aussie Taipan was overtaking a whole fleet of 18 and 20 foot catamarans in a 1999 US distance race.

Wouter